Speaking of immigration, I suspect that European immigration to Africa will be VERY messy. Probably worse than US immigration to Latin America.
And also a lot of Latinos either are completely European-descending or have European features including being light-skinned. So you can't necessarily differentiate a US white person, from a Mexican with prominent European ancestry just by looking at their faces.
Likewise, African-Americans can try to pass as Afro-Latinos.
In other words, most US citizens have a chance to pass as locals (at least if they dress and behave like locals, and learn to speak Spanish without accent).
While, in Subsaharan Africa, it's completely impossible for Europeans to visually blend in.
Plus, it's easier to learn Spanish or Portuguese as an English-speaker, than to learn Arabic (or Subsaharan Africa languages) as an European, as English, Spanish and Portuguese are already "cousin" languages deriving from Latin, while African languages and Arabic are completely separate.
Also, Islam is the dominant religion of North and Western Africa, while European immigrants will either be Christians, or atheists/agnosticists with a Christian cultural background.
Overall, US citizens will have a real chance to pass as locals in Latin America (because 1 : there are many Latinos, either white or black, that already look similar to US citizens ; 2 : they have the same religion, or close enough if you overlook the Catholic / Protestant differences ; 3 : they have relatively similar languages).
European immigrants in North and Western Africa, on the other hand, will be stuck as the "eternal foreigners" that just can't blend in, because (1 : they look completely different from locals, at least in Subsarahan Africa ; 2 : they have a very different language and will struggle to learn the local language ; 3 : they have a different religion).
And also...
While there was dislike of the USA in Latin America, because of the support of tinpot dictators and economical imperialism, at least the USA never directly colonized or occupied continental Latin America (except for Panama).
Many European immigrants, on the other hand, will have to go to the specific countries that their own country colonized or occupied in the recent past.
Such as, Italians going to Libya (former colony) or Tunisia (that they occupied briefly in 1942-43), French going to Tunisia and Algeria, and of course Europeans (including a lot of French people) managing to reach Western and Central Africa (which was mostly a big French colony).
And in those African countries, a LOT of people (in their 30s to 60s) are old enough that they were already alive at the time of colonization and actually remember it (or even WWII Italian occupation for Tunisia), but young enough to still be dangerous and violent if they want to.
While the vast majority of people would never commit violent crimes, I expect a small but dangerous minority of individuals to take their revenge for colonial crimes on disgruntled European refugees.
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Just as messy, would be the Soviet immigration, mostly towards Iran (every other bordering country either was itself nuked, or hates Russia, or both). Especially with Iran being an Islamic Republic, and a lot of people remembering the stunt that Stalin pulled in 1946 (when he basically tried to take over northern Iran), and the WWII occupation.